A right-leaning think tank has brought what it believes is the most comprehensive constitutional challenge to a law that gives preference to American Indian families in adoptions of Indian children.

The Goldwater Institute says the Indian Child Welfare Act of 1978 has outlived its purpose, doesn't consider what's in the best interest of the child and discriminates based on race.

Congress passed the law after high numbers of Indian children were removed from their homes and placed with non-Indian caretakers. It gives the child's tribe and family a say in decisions affecting the child.

The lawsuit filed in U.S. District Court in Arizona seeks class-action status.

The U.S. Bureau of Indian Affairs didn't immediately respond to a request for comment Tuesday. The Arizona Department of Child Safety declined to comment.